

public class HashBuck2<K,V> {
    static class Node<K,V>{
        public K key;
        public V value;
        public Node<K,V> next;
        public Node(K key,V value){
            this.key=key;
            this.value=value;
        }
    }
    public Node<K,V> [] array;
    public int usedSize;
    public HashBuck2(){
        array=(Node<K,V>[])new Node[10];
    }
    public static final double Lode_factor=0.75;
    public void push(K key,V value){
        int hash=key.hashCode();
        int index=hash%array.length;
        Node<K,V> cur=array[index];
        while (cur!=null){
            if (cur.key.equals(key)){
                cur.value=value;
                return;
            }
            cur=cur.next;
        }
        //头插法
        Node<K,V> node=new Node<>(key,value);
        node.next=array[index];
        array[index]=node;
        usedSize++;
        if(calcLodeFactor()>=Lode_factor){
            resize();

        }
    }

    private void resize() {
        //先定义一个新的数组
        Node<K,V>[] newArray=(Node<K,V>[])new Node[2*array.length];
        //遍历array数组
        for (int i = 0; i < array.length; i++) {
            Node<K,V> cur=array[i];
            while (cur!=null){
                int newIndex= cur.key.hashCode()% newArray.length;
                Node<K,V> curN=cur.next;
                //头插法
                cur.next=newArray[newIndex];
                newArray[newIndex]=cur;
                cur=curN;
            }
        }
        array=newArray;
    }
    public V get(K key){
        int hash=key.hashCode();
        int index=hash%array.length;
        Node<K,V> cur=array[index];
        while (cur!=null){
            if (cur.key.equals(key)){
               return cur.value;
            }
            cur=cur.next;
        }
        return null;
    }

    private double calcLodeFactor() {
        return usedSize*1.0/array.length;
    }
}
